Replaceable wear components for percussion tools

ABSTRACT

A piston actuated drilling tool includes a casing and a guide sleeve disposed within the casing in proximity to the top end of the casing. A piston is slidably disposed within the casing for reciprocating movement therein. The piston has a nose end arranged to reciprocate within the guide sleeve, wherein a first wear area of the tool occurs between the piston nose end and the guide sleeve. A replaceable wear bushing assembly is located within the guide sleeve at the first wear area. The replaceable wear bushing assembly can include either a static wear bushing or a sliding wear bushing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of U.S. Provisional Application No.62/483,808, filed Apr. 1, 2015, which the entirety thereof isincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to replaceable wear components subject tosliding friction abrasion in down-the-hole tools, such as pistonactuated drilling tools, although not exclusively, to percussion toolsfor downhole drilling.

BACKGROUND

Drilling in rock can be performed by percussive drilling, which is acombination of percussion and rotation. Percussive drilling anddown-the-hole drilling (DTH) present difficulties with regard to repairand maintenance.

Percussive drilling and DTH tools use a piston assembly that slidablyoscillates against, or relative to, non-moving components. The toolcomponents create wear at specific locations. Over time this wear causesinternal clearances to increase such that leakages increase, whichreduce pressure and, therefore, operational efficiency of the pistonsystem. In the above-described drilling tool, individual parts may beworn, but to replace such worn parts the entire assembly must bereplaced.

Customarily, with percussive drilling and DTH hammer assemblies, theparts are inspected and when necessary replaced, which often involvesrebuild. This process is time consuming and increases EHS risks,shipping, and inventory.

SUMMARY

The present disclosure provides a system of replaceable components athigh wear areas in a percussion tool. In order to reduce costs andincrease turn-around time, the components in the high wear areas can bereplaced improving percussion efficiency closer to design standard. Thecomponents are low cost and light weight reducing service costs andeffort supporting tool maintenance. The replaceable components can bedesigned into the system so that only those components are replacedduring service.

Further improvements are made by use of sliding wear bushing componentsthat slightly increases pressure thereby offsetting ongoing losses dueto increasing clearances.

One area of wear requires sliding and impact protection. This can beachieved by a replaceable sleeve held in place by friction or othermechanical fastening methods.

The sleeve may be combined with surface lubrication/corrosion protectionand/or coated with modified surface properties.

An alternate embodiment includes a sleeve that may slide with respect tothe guide sleeve in order to alter pressure and/or timing events of thepiston, as wear in all locations allows additional leakage and therebyreducing designed power. Slight vertical axial movement of thereplaceable sleeve will alter pressure and timing on the up and downstrokes. Sleeve material may be polymer, ferrous, and non-ferrous.

Another wear area requires sliding protection without additional drag orscraping against the casing wall. This is most economically achieved byuse of rings fitted to special grooves pre-machined into the pistonouter diameter. The rings are specially designed to improve sealing ofthe worn faces while not increasing drag resistance of the ring tocasing wall, which cannot be 100% prevented, decreases power bydecreasing velocity of the piston. Multiple rings may be used on asingle piston. Ring material may be polymer, ferrous, and non-ferrous.

In order to reduce cost and increase turn-around time the areasmentioned above can be repaired sufficiently and quickly by usingreplaceable elements specifically designed for these locations.

Accordingly, the present piston actuated drilling tool includes a casinghaving opposed top and bottom ends and an inner surface. A guide sleeveis disposed within the casing in proximity to the top end of the casing.The guide sleeve has an inner surface and an outer surface, the outersurface of the guide sleeve contacting the inner surface of the casing.A piston slidably is disposed within the casing for reciprocatingmovement therein, the piston having a nose end arranged to reciprocatewithin the guide sleeve, wherein a first wear area of the tool occursbetween the piston nose end and the guide sleeve. A replaceable wearbushing assembly is located within the guide sleeve at the first weararea.

The foregoing summary, as well as the following detailed description ofthe embodiments, will be better understood when read in conjunction withthe appended drawings. It should be understood that the embodimentsdepicted are not limited to the precise arrangements andinstrumentalities shown.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a longitudinal cross-section of a rotary percussion tool.

FIG. 1B is an enlarged section of the tool of FIG. 1A.

FIG. 2 is a front view of a solid static bushing according to thepresent disclosure.

FIG. 3 is a perspective view of a split static bushing according to thepresent disclosure.

FIG. 4 is a front view of a static gland seal according to the presentdisclosure.

FIG. 5 is a cross-sectional view of the replaceable wear bushingassembly according to the present disclosure.

FIG. 6 is a cross-sectional view of a drilling tool incorporating thereplaceable wear bushing assembly of FIG. 5 .

FIG. 7 is a cross-sectional view of another embodiment of a replaceablewear bushing assembly of the present disclosure incorporating a slidingwear bushing.

FIG. 8 is an enlarged view of the bushing assembly of FIG. 7 .

FIG. 9 is an enlarged cross-sectional view of another bushing assemblyhaving a split ring seal.

FIG. 10 is a perspective view of the split ring of FIG. 9 .

FIG. 11 is an enlarged view of a split ring and spacer ring incorporatedin another embodiment of a sliding wear bushing of the presentdisclosure.

FIG. 12 is a cross-sectional view of the sliding wear bushing assemblyof FIG. 11 .

FIG. 13 is a perspective view of a piston having sealing rings accordingto the present disclosure.

FIG. 14 is an enlarged cross-section of the piston of FIG. 13 positionedwithin a drilling tool.

FIG. 15 is a perspective view of the piston ring of FIGS. 13 and 14 .

FIG. 16 is an enlarged cross-section of the ends of the ring.

FIG. 17 is another embodiment of the piston ring having overlappingends.

FIG. 18 is an enlarged side view of the overlapping ends of the ring ofFIG. 17 .

DETAILED DESCRIPTION

Referring to FIG. 1A, a piston actuated DTH drilling tool 10 includes acasing or housing 12 having opposed top and bottom ends. A drive sub 14is threadedly mounted to the bottom/drive end 11 of the casing 12. A topsub 16 is threadedly coupled to the top end 9 of the casing 12. A piston20 is movably disposed within casing 12. Piston 20 includes a choke 30and a nose end 21. As is well known, the movement of piston 20 isregulated by the timing of pressure between fluid chambers formed in thecasing. The drive sub 14 includes one or more annularly shaped drivelugs 26 that are stacked on top of one another and a portion of amandrel 22. The mandrel 22 is a substantially solid component to which adrill bit (not shown)can be attached to. The mandrel 22 is axiallymoveable with respect to both the casing 12 and the drive sub 14, aportion of the mandrel 22 being inserted and housed within the casing12. The top sub 16 is threadedly connected to a drill string (notshown), which is connected to a rotation motor on a drilling rig at thesurface. Rotational torque is then applied through the rotating assemblyincluding casing 12, drive sub 14, drive lugs 26, and mandrel 22.

FIG. 1B illustrates two areas of wear, wear area 1 (WA₁) and wear area 2(WA₂). WA₁ occurs between the head 36 of the piston and shoulder 38 ofguide sleeve 18. WA₂ occurs between inner surface 13 of casing 12 and anouter surface of 23 of piston 20. Guide sleeve 18 has inner surface 17and outer surface 19.

Wear primarily occurs along these two areas for separate reasons. Atarea WA₁ the piston is slidably entering the guide sleeve, repeatably,along with any entrainments in the motive force and lubrication causingboth sliding wear and contact wear as the piston moves about its centralaxis. At area WA₂ the large diameter of the piston is sliding againstthe large diameter casing along with any entrainments in the motiveforce and lubrication exciting wear on both surfaces.

FIGS. 2-5 refer to a replaceable wear bushing assembly 50 (FIG. 5 ).Assembly 50 includes a solid static annular/ring-shaped bushing 52 and astatic gland seal 60, which can be provided to provide protection at WA₁(FIG. 1B). As shown in FIG. 2 , bushing 52 can be a solid static bushingmade of a ferrous or non-ferrous metal. Bushing 52 can be a drop inreplaceable insert that is also reversible.

Alternatively, as shown in FIG. 3 , the bushing can be a split staticbushing 52′ that is split at cut 48. Splitting the static bushing easesinstallation. Often rust can occur at the interface between bushing 52and the guide sleeve 18, so splitting the bushing can also ease removal.Bushing 52 can include indents or holes 51, which snap ring pliers oranother tool can fit with to assist with installation or removal. Itshould be appreciated that solid static bushing 52 can also include theindents or holes to assist with install/removal.

Outer and inner surfaces 53, 55 of static bushing 50, 50′ can be coatedor treated with a secondary heat treatment process to increase wearresistance, hardness, lubricity, modify properties or a combination ofany/all.

Referring again to FIGS. 2 and 3 , static bushing 52, 52′ includes anupper portion 56, upper shoulder 58, lower portion 54 and a lowershoulder 59. As will be explained further herein, upper shoulder 58 isarranged to support and retain static gland seal 60 and lower shoulder59 is provided to locate the bushing in guide sleeve 18. Gland seal 60prevents bushing 52. 52′ from interfering with the top sub assembly dueto it retaining bushing position. Seal 60 also provides some amount ofsealing by preventing water from seeping between the bushing and guidesleeve' It should be appreciated that the bushing can be held in placeby friction or other mechanical fastening methods.

Referring to FIGS. 4 and 5 , static gland seal 60 is ring shaped and hasan inner diameter 62 that corresponds to the outer diameter of upperportion 56 of static bushing 52, 52′. Gland seal 60 can be a ferrous,nonferrous, elastomer or rubber element that holds bushing 52, 52′inplace. Upper shoulder 58 supports gland seal 60. Due to bushing havingboth shoulders 58, 59, as set forth above, the bushing is reversible,i.e., lower portion 54 would become an upper portion and lower shoulder59 would support seal 60.

Gland seal 60 includes a rib 64 that provides sealing for the interfacegaps between bushing 52, 52′ and guide sleeve 18. Gland seal 60 furtheraids installation effectiveness by visual and tactile reinforcement.

As shown in FIG. 5 , static bushing 52 has a height H. Height H iscritical as the bushing cannot extend above the guide sleeve. Bushing 52come in differing sectional length/heights to compensate for low toheavy wear conditions.

Height H cannot interfere with the top sub 16, when installed, andsimultaneously provide the timing event as the piston moves up and down.The timing event is controlled at the inside edge of bushing 54 (or 56when reversed as described further herein). These edges are controlledby H and located by the shoulders 58/59 and held in place by friction,gland seal 60, or other mechanical retention.

As shown in FIG. 6 , static bushing 52 is positioned such that guidesleeve 18 is protected from wear by piston head 36 at WA₁. Thus, bushingassembly 50 provides sliding and impact protection. Outer surface 17contacts inner surface 53 of guide sleeve 18.

An alternate embodiment of the bushing assembly is shown in FIGS. 7 and8 , wherein the bushing may slide with respect to the guide sleeve 18 inorder to alter timing and pressure at that point and to prevent wear inall locations that would allow additional leakage and thereby reducingdesigned power.

Sliding wear bushing 70 includes a gland seal 80 in the shape of a wiperhaving legs 82, 84, and a spring mechanism 90. Sliding bushing 70 may bepolymer, ferrous, and non-ferrous material. Sliding bushing 70 includesan upper portion 72 with an upper shoulder 74 and a lower portion 76having a lower shoulder 78.

Gland seal 80 is supported by upper shoulder 74 of sliding bushing 70and extends into indentation 66 formed in guide sleeve 18 such that legs82, 84 of seal 80 are delimitated by indentation 66 and shoulder 74.Gland seal 80 can be made of a flexible material such as polymer,elastomer, or ferrous or non-ferrous metals.

Spring mechanism 90 is arranged at the lower portion 76 of slidingbushing 70 and extends between a shoulder 68 of guide sleeve 18 andlower shoulder 78. Spring mechanism 90 can be a ring of polymer,elastomer, or soft ferrous or non-ferrous metals.

As will be described further herein, sliding bushing 70 can also bereversible within guide sleeve 18. In the reversed position bushing 70is used without spring 90 and hence becomes a static bushing.

Spring mechanism 90 provides enough force to compensate for pistonpressure to allow sliding bushing 70 to move within the guide sleeve 18.

Due to components 80 and 90, bushing 70 can slide within guide sleeve18. Slight vertical axial movement of the replaceable bushing will altertiming events on the up and down strokes providing an increase inpressure to offset leakage.

In another embodiment, in lieu of gland seal 80, a split ring 98 can beused. Referring to FIGS. 9 and 10 , a split ring 98 can be positionedwithin indentation 66 of guide sleeve 18. Split ring 98 can be made of apolymer, ferrous or non-ferrous metal.

In another embodiment as shown in FIGS. 11 and 12 , split ring 98 andsliding wear bushing 70 can be used in conjunction with a spacer ring100. Spacer ring 100 acts as a retention ring to keep bushing 70 in astatic position, i.e, bushing 70 is prevented from sliding. Spacer ring100 can be an elastomer, polymer, ferrous or non-ferrous material.Additionally, as described above, spacer ring 100 can be coated ortreated with secondary heat treatment process(es) to increase wearresistance, hardness, lubricity or a combination of all or some.

As shown in FIGS. 11 and 12 , sliding bushing 70 can be disposed inguide sleeve 18 in an inverted position from that as shown in FIGS. 7and 8 . In other words, lower portion 76 of the bushing is now at theupper side at indentation 66 of guide sleeve 18 and upper portion 78 isnow located at the lower side at shoulder 68 of guide sleeve 18. Spacerring 100 in positioned between split ring 98 and shoulder 74 of bushing70.

By inverting bushing 70 as described above, the timing point is nowstatic. Inverting also provides a new surface for the timing points aswear occurs during use. When the dynamic bushing is used (eitherinstalled new from manufacturing or during repair) and depending on theamount of wear on the piston surfaces it may be desirable to use thedynamic bush in the static position first for a period of operatinghours and then flip the bushing into dynamic mode. Flipping the bushingin either direction provides a new wear surface with decreased clearancebetween piston and bushing.

Accordingly, sliding wear bushing 70 can be turned into a static bushingby i) inverting/turning the bushing upside down, and ii) adding spacerring 100.

Wear area 2 requires sliding protection without additional drag orscraping against the case wall. This is most economically achieved byuse of rings fitted to special grooves pre-machined into the pistonouter diameter. The rings are specially designed to improve sealing ofthe worn faces while not increasing drag resistance of the ring tocasing wall, which cannot be 100% prevented, decreases power bydecreasing velocity of the piston. Multiple rings may be used one asingle piston. Ring material may be polymer, ferrous, and non-ferrous.

However, as set forth above, wear area 2 (WA₂) (FIG. 1B) also requiressliding protection without additional drag or scraping against the casewall. As will be described further below, this is most economicallyachieved by use of rings fitted to special grooves pre-machined into thepiston outer diameter. The rings are specially designed to improvesealing of the worn faces while not increasing drag resistance of thering to casing wall, which cannot be 100% prevented, decreases power bydecreasing velocity of the piston. Multiple rings may be used one asingle piston.

Referring to FIGS. 13-18 , a plurality of piston sealing rings 110 areprovided to protect the piston 20 from wear in area (WA₂) (FIG. 1B).Piston sealing rings 110 are located in grooves 104 formed in an outersurface 102 of piston 20. Referring to FIG. 14 , piston sealing ringsmake up the gap between the body of piston 20 and the inner surface ofcasing 12 to minimize leakage. Piston sealing ring material can be anelastomer, polymer, ferrous, nonferrous materials and may be coated orsecondary heat treatment to improve hardness, lubricity, or wearresistance.

As shown in FIG. 15 , piston sealing rings 110 are split for aidinginstallation during assembly. However, it should be appreciated that thefit of rings 110, piston 20 and casing 12 must be tightly controlled tominimize movement while ensuring a proper outer diameter of the piston.A fitment allowing for slight decreases in the outer diameter of thepiston 20, as the inner wall of casing 12 may not have even wear alongpiston travel, is tolerable, though not preferred.

Ends 112, 114 of piston sealing ring 110 can be overlapping as shown inFIG. 16 . Alternatively, ends 112, 114 can overlap as shown in FIGS. 17and 18 .

It is also desirable that piston sealing rings 110 do not exert force onthe inner surface of the bore of casing 12, as such may impede pistontravel and velocity. The size of piston sealing rings 110 are designedto add sealing diameter to the piston bringing it back to designtolerances.

As the piston and case wear during use the clearance between the pistonouter diameter and case wall 12 will increase and at times may besubstantial. It may not be desirable or economical to replace eithercomponent in remote locations, lack of inventory, or if tool end of lifeis expected soon. The rings are designed to predict and fill the amountof clearance that might occur during use. Material selection should bemade to balance rigidity, abrasion resistance, and flexibility. Thematerial must be flexible enough to allow installation around the pistonand slight movement perpendicular to the piston axis as the pistontravels up and down. Commonly purchased off the shelf O-rings are notthe correct size to fill the close clearance gap between piston and caseplus the elastomer friction coefficient is too high when it contacts thecase wall. The standard O-ring also stretches in the installed positionand the actual OD of a stretched O-ring will be too large/smalldepending on the molding tolerance of the O-ring.

Rings 110 are replaceable with varying cross-sectional size to customfit the worn piston body as piston wear in service may vary.

Cross-sectional geometry of rings 110 may vary for commonly availablematerials. Rings have a mainly semi-circular cross section to locate onthe piston and remain in place during operation. The flat side of thesemi-circle will slide in close proximity to the case wall.

Although the present embodiment(s) has been described in relation toparticular aspects thereof, many other variations and modifications andother uses will become apparent to those skilled in the art. It ispreferred therefore, that the present embodiment(s) be limited not bythe specific disclosure herein, but only by the appended claims.

What is claimed is:
 1. A piston actuated drilling tool comprising: acasing having opposed top and bottom ends and an inner surface; a guidesleeve disposed within the casing in proximity to the top end of thecasing, the guide sleeve having an inner surface and an outer surface,the outer surface of the guide sleeve contacting the inner surface ofthe casing; a piston slidably disposed within the casing forreciprocating movement therein, the piston having a nose end arranged toreciprocate within the guide sleeve, wherein a first wear area of thetool occurs between the piston nose end and the guide sleeve; and areplaceable wear bushing assembly located within the guide sleeve at thefirst wear area.
 2. The drilling tool of claim 1, wherein the wearbushing assembly includes a static wear bushing, the nose end of thepiston reciprocating within the static bushing.
 3. The drilling tool ofclaim 2, wherein the static wear bushing is a solid piece.
 4. Thedrilling tool of claim 2, wherein the static wear bushing is a splitring.
 5. The drilling tool of claim 2, wherein the static wear bushingis a polymer, ferrous, or non-ferrous material.
 6. The drilling tool ofclaim 2, wherein the wear bushing assembly includes a static gland sealdisposed between an outer surface of the static wear bushing and theinner surface of the guide sleeve.
 7. The drilling tool of claim 6,wherein the gland seal is made of a flexible material such as polymer,elastomer, rubber or ferrous or non-ferrous metals.
 8. The drilling toolof claim 1, wherein the inner and outer surfaces of the wear bushing arecoated or heat treated.
 9. The drilling tool of claim 1, wherein thewear bushing assembly includes a sliding wear bushing arranged to movewithin the guide sleeve, the nose end of the piston reciprocating withinthe sliding wear bushing.
 10. The drilling tool of claim 9, wherein theposition of the sliding wear bushing within the guide sleeve can beinverted to change the sliding wear bushing to a static bushing.
 11. Thedrilling tool of claim 9, wherein the inner and outer surfaces of thesliding wear bushing are coated or heat treated.
 12. The drilling toolof claim 9, wherein the wear bushing assembly includes a gland seallocated at one end of the sliding wear bushing and a spring mechanismlocated at another end of the sliding wear bushing, both the slidinggland seal and the spring mechanism being disposed between an outersurface of the sliding wear bushing and the inner surface of the guidesleeve.
 13. The drilling tool of claim 12, wherein the gland sealincludes a pair of legs.
 14. The drilling tool of claim 12, wherein thegland seal is made of a flexible material such as polymer, elastomer,rubber or ferrous or non-ferrous metals.
 15. The drilling tool of claim9, wherein the wear bushing assembly includes a split ring located atone end of the sliding wear bushing, the split ring being disposedbetween an outer surface of the sliding wear bushing and the innersurface of the guide sleeve.
 16. The drilling tool of claim 15, furthercomprising a spacer ring positioned between the split ring and ashoulder of the sliding bushing, the spacer ring being arranged as aretention ring to keep the sliding wear bushing in a static position.17. The drilling tool of claim 16, wherein the spacer ring and splitring are made of polymer, elastomer, rubber or ferrous or non-ferrousmetals.
 18. The drilling tool of claim 1, wherein a second wear area ofthe tool occurs between the inner surface of casing and the outersurface of the piston, the outer surface of the piston including atleast one groove and a piston ring provided in the at least one grooveand arranged to protect the piston from wear in the second wear area.19. The drilling tool of claim 18, wherein the at least one piston ringhas overlapping ends.
 20. A piston actuated drilling tool comprising: acasing having opposed top and bottom ends and an inner surface; a guidesleeve disposed within the casing in proximity to the top end of thecasing, the guide sleeve having an inner surface and an outer surface; apiston slidably disposed within the casing for reciprocating movementtherein, the piston having a nose end arranged to reciprocate within theguide sleeve, wherein a first wear area of the tool occurs between thepiston nose end and the guide sleeve; a sliding wear bushing arranged tomove within the guide sleeve; a gland seal located at one end of thesliding wear bushing; and a spring mechanism located at another end ofthe sliding wear bushing, both the sliding gland seal and the springmechanism being disposed between an outer surface of the sliding wearbushing and the inner surface of the guide sleeve